Brake device for hypodermic jet injector



July 28, 1970 5. I. YAHNER BRAKE DEVICE FOR HYPODERMIC JET INJECTOR Filed Nov. 13, 1967 m mm l 9% mm Nu NM mm F E ms 11 w @w H QN m w wmw swwm 9% N% ww W Q P WN M I? Z/ n for. 611567? f. lfiner United States Patent 3,521,633 BRAKE DEVICE FOR HYPODERMIC JET INJECTOR Gilbert 1. Yahner, East Detroit, Mich., assignor to R. P. Scherer Corporation, a corporation of Michigan Filed Nov. 13, 1967, Ser. No. 681,990 Int. Cl. A61m 11/06 US. Cl. 128173 4 Claims ABSTRACT OF THE DISCLOSURE A drag brake for a hypodermic jet injector of the type having a nonrotatable cylindrical housing with a discharge nozzle attached to one end of the housing and a rotatable cocking barrel attached to the other end of the housing. The brake is an arcuately shaped and biased wire fixed in a slot at the barrel end of the housing. The wire is biased outwardly against the sides of the barrel which rotates around the outer surface of the housing. The friction of the biased wire against the rotatable barrel provides a braking effect sufiicient to prevent the rotatable barrel from unintentionally rotating.

BACKGROUND OF THE INVENTION This invention relates to the improvement in a hypodermic jet injector of a drag brake.

The use of a hypodermic jet injector for administering vaccines or the like has become increasingly popular. A typical hypodermic jet injector construction is illustrated in Pat. No. 3,330,276 issued to Gordon on July 11, 1967.

In such a hypodermic jet injector, a spring-driven plunger forces a measured amount of medicament through a discharge orifice and through the skin of a patient. In order to cock the plunger, the driving springs must be compressed. This is accomplished by attaching a rotatable barrel to the endof the cylindrical housing containing the compressible spring. The barrel is then rotated in the counterclockwise or clockwise directions to drive a threaded rod which. in turn, compresses the plunger driving springs. The details of this construction are more fully set forth in the description which follows.

The problem encountered with a mechanism of this type is that after extended use of the hypodermic jet injector unit, the threads on the rod, which is used to compress the springs, become worn. Consequently the rotatable barrel has a tendency to unwind due to the compressive force of the power springs acting on the worn threads. This causes the entire unit to become deactivated. Simultaneously with becoming deactivated, the jet injector unit causes medicament to be discharged from the nozzle orifice and wasted. Thus some means is necessary to prevent the rotatable barrel from unwinding, especially after prolonged use of the injector unit.

SUMMARY OF THE INVENTION In a principal aspect the present invention comprises the improvement in a hypodermic jet injector, of the type having a non-rotatable cylindrical housing with a rotatable barrel attached at the power input end of the cylindrical housing, of a drag brake which frictionally inhibits the rotation of the barrel about the housing.

It is thus an object of the present invention to provide the improvement in a hypodermic jet injector unit of a drag brake.

It is a further object of the present invention to provide a drag brake which is economically manufactured and easily installed in present types of hypodermic jet injector units with a minimum of modification required.

These and other objects, advantages and features of f f 3,521,633 Patented July 1970 the present invention will be more fully set forth in the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWING In the description of the drawing which follows reference will be made to the following figures:

FIG. 1 is a side cross-sectional view of a typical hypodenmic jet injector unit including the improvement of a drag brake;

FIG. 2 illustrates the improvement of a drag brake in a cross-sectional view taken substantially along the line 2-2 in FIG. 1; and

FIG. 3 is a plan view of the drag brake before insertion into the hypodermic jet injector unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the improved hypodermic jet injector unit in a cross-sectional view. The unit has the general appearance of an elongated body which includes a cylindrical housing 10 that is enclosed at the forward end by a front sleeve 12 which is threadedly connected thereto. At the opposite or rear end of the housing 10, a winding sleeve or barrel 14 is rotatably connected to the housing 10. The barrel 14 includes an inturned flange 16 which cooperates with an annular ridge 20 of the housing 10 in order to prevent longitudinal movement of the housing 10 and the barrel 14.

A latch housing 22, which also serves as a bearing support for a thrust bearing 24 is threaded into the rear end of the barrel 14. The thrust bearing 24 is interposed between the latch housing 22 and the cylindrical housing 10 in order to permit rotation between the parts. A release button cap 26 is securely fastened to the latch housing 22 by means of a conventional nonreversible, bayonet type connection. The cap 26, the barrel 14, and the latch housing 22 are all rotatable together, the barrel 14 being locked to the housing 22 by means of a key 28 which fits into a slot 30 provided in the housing 22 and the barrel 14.

The cylindrical housing 10 is locked to the forward sleeve 12 in order to prevent rotation therebetween by means of a latch 32, which is adapted to fit into a series of longitudinal slots 34 provided in the inner surface of the front sleeve 12. A spring 36 biases the latch 32 outwardly. The cylindrical housing 10 includes a series of blind, axially extending openings 38 which are spaced circumferentially in the housing 10. Although single springs may be inserted into the openings 38, the springs are preferably used in pairs, the internal springs 40 being of a smaller diameter and of opposite helix to the external springs 42. Pins 44 are located concentrically of the springs 40 and 42 and extend through the openings 38 in order to prevent the buckling of the springs 40 and 42 within the openings 38. The forward ends of the springs seat in recesses 46 provided in a nut 48, the recesses 46 being concentric with the openings 38.

The nut 48 includes a sleeve-like extension 50 which projects rearwardly in the bore 52 of the housing 10. The extension 50 is prevented from rotational movement within the cylindrical housing 10 by suitable means, as a key (not shown). The bore 52 is internally threaded and is adapted to threadedly receive the lifting screw 54. Thus, upon rotation of the screw 54, the nut 48 is pulled rearwardly to thereby compress the springs 40 and 42 and load the injector.

A latch mechanism is provided for locking the lifting screw against axial movement until such time as the springs 40 and 42 are released for injecting the medicament. Latch wedges 58 project through opening 60 pro vided in the latch housing 22 and are adapted to engage the fins 62 at the rear end of the lifting screw 54. The

release button 56 includes an inwardly turned flange 64 which is adapted to bear against the outer ends of the latch wedges 58 to normally prevent them from retracting into the groove 66 of the latch housing 22. The release button 56, upon depression, causes the side walls to move forwardly into the groove 70 of the latch housing 22 against the compression of the spring 68 whereupon the groove 66 in the sidewall of the button 56 becomes aligned with the openings 60 in the latch housing 22. Due to the slope on the bottom of the wedges 58, they move outwardly into the groove 66 to thereby release the lifting screw 54.

A valve housing member 72 is threadedly attached to the front end of the front sleeve 12. Defined within the valve housing member 72 is a bore 74 which is concentric with the plunger head 76 of the ram 78. The ram 78 is fixed to the nut 48. A rotatable valve 80 is fixed in the housing member 72 in the passageway 82 leading from the bore 74 to the medicament discharge nozzle 84. A medicament container 86 is suitably positioned on the jet injector by means of the brace 88. A tube 90 leads from the container 86 to the valve 80.

In operation the plunger head 76 is drawn to the left in FIG. 1 with the valve 80 rotated 90 from its position illustrated in FIG. 1. This draws a dose or charge of medicament from the container 86 into the bore or chamber 74. The valve 80 is then rotated to the position shown in FIG. 1 whereupon the button 56 may be depressed to release the wedges 58 thereby causing the springs 40 and 42 to drive the ram 78 and plunger head 76 into the bore 74 and thereby drive the medicament through the valve 80 and the passageway 82 out through the nozzle 84.

The charging and discharging operation is accom plished by winding a crank 92 in the clockwise and counterclockwise directions. Assuming that medicament has just been discharged and the valve 80 rotated into a position leading from the container 86 into the bore or chamber 74, the barrel 14 is turned in a counterclockwise direction in order to move the lifting screw 54 rearwardly. As the end of the screw contacts and compresses the spring 68, the release button 56 moves rearwardly and wedges 58 are forced out of the groove 66. The wedges 58 then move underneath the fins 62 of the lifting screw 54 in order to latch the screw 54. At this time the spring 68 snaps the release button 56 to the loading position.

The barrel 14 is then rotated in a clockwise direction in order to turn the screw 54 in the bore 52 and to thereby move the nut 48 rearwardly and compress the springs 40 and 42. As the nut 48 moves rearwardly, the ram 78 and plunger head 76 also move rearwardly. As the plunger 78 moves rearwardly, medicament flows from the container 86 through the tube 90 and the valve 80 and finally into the bore or chamber 74. When the desired amount of loading is obtained the winding of the barrel 14 is stopped and the valve 80 is rotated to the position shown in FIG. 1.

What has been described above is old and well-known in the art. In FIG. 1, as set forth above the springs 40 and 42 are in a state of compression and medicament is ready to be discharged. It has been found that when the component parts of the jet injector have been in service for a period of time that the threads on the screw 54 and the bore 52 become worn and lose their ability to hold the springs 40 and 42 in a wound up or power position. Thus it has been found that although the springs 40 and 42 are wound after service the entire barrel 14 will be caused to rotate by the power of the compression in the springs 40 and 42. This causes medicament to flow from the nozzle 84 before the button 56 has been pressed. Not only does this diminish the effectiveness of the jet injector but it also wastes medicament.

The improvement of the present invention as illustrated in FIG. 1 is to provide a circumferential slot 94 in the outer surface of the end portion or ridge 20 of the cylindrical housing 10. A biased segment of spring or wire 96 is then inserted into the slot 94. The spring 96 is arcuately shaped and is biased away from the center of the arc. The spring 96 frictionally engages the barrel 14 and drags or inhibits its rotation. This drag is especially important when the injector is in the wound-up or cocked position.

FIGS. 2 and 3 illustrate the preferred configuration of the spring 96. It is arcuately shaped with the ends being bent in any desired configuration. In the presently preferred embodiment the spring 94 has its respective ends 104 and 106 bent in a shape adapted to engage indentations 98 and 102 in the slot 94. Thus the spring 96 is held in a fixed position in the slot 94 of the housing 10. While fixedly engaging the housing 10, because it is arcuately shaped and biased away from the center of the arc, spring 96 simultaneously slidably engages the barrel 14. The friction between the wire 96 and the barrel 14 thus prevents the barrel 14 from freely rotating and thereby prevents unwanted unwinding of a cocked jet injector.

Preferably the spring 96 is fabricated from a Phosphor bronze, spring tempered wire material. While two indentations 98 and 102 have been shown, this feature should not be limiting since more or less than two indentations may be used. Likewise the fact that the indentations are defined in the housing 10 should not be limiting, since, for example, the spring may be fixedly mounted on the housing 10 and biased to frictionally engage the barrel 14 or may be engaged in indentations in the barrel 14 and spring loaded to frictionally engage the housing 10.

What is claimed is:

1. In a hypodermic jet injector of the type having a non-rotatable cylindrical housing, said housing including a medicament discharge end and a power input end with an outer surface, said power input end including attached thereto a rotatable cocking barrel slidably engaging said outer surface such that said cocking barrel upon rotation provides the means to supply power to said jet injector for discharge of measured doses of medicament, the improvement of a drag brake which frictionally inhibits rotation of said barrel about said housing, said brake being arcuate in shape and being inserted between said barrel and said housing at the outer end surface of said housing to frictionally engage said barrel along an arcuate portion thereof such that said barrel is manually rotatable and will not rotate due to force from said means to supply power to said injector.

2. The improvement of claim 1 wherein said brake is substantially fixedly attached to said housing and frictionally engages said rotatable barrel.

3. The improvement of claim 2 wherein said outer end surface includes circumferential slot with at least one indentation in said slot, and said brake comprises an arcuately shaped spring wire, biased away from the center of the are, said wire including at least one bend, said wire being inserted in said slot with said bend engaging said indentation to hold said wire in a fixed relation with respect to said housing.

4. The improvement of claim 3 wherein said wire has a first and second end, each end having a bend and said slot has first and second indentations to engage said first and second bends.

References Cited UNITED STATES PATENTS 2,465,213 3/1949 Dressel 18883 XR 2,514,264 7/1950 Soper l8883 2,754,818 7/ 1956 Scherer. 3,330,276 7/ 1967 Gordon.

WILLIAM E. KAMM, Primary Examiner US. Cl. X.R. 188-83 

